This section provides background information related to the present disclosure which is not necessarily prior art. This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.
Approximately 20% of all car crashes in the United States (nearly 1,250,000 per year) are weather-related. From these crashes, on average, nearly 6,000 people are killed and over 450,000 people are injured.
The principles of the present teachings provides a simple method and apparatus to distinguish road conditions (i.e. wet roads from icy roads) which is used to warn drivers, provide data for automobile traction control system, and provide data for autonomous automobile systems.
Dry roads can be distinguished unambiguously from other road conditions (such as icy roads, wet roads, and snow covered roads) using measurements of the radiance in spectral bands in which the slope of the absorption of electromagnetic radiation by ice is substantially different from that of water. According to the principles of the present teachings, multi-spectral cameras can be used to detect parameters sufficient for surface monitoring, such as but not limited to ice detection on aircraft, manufacturing systems, or other objects of interest.
The present teachings provide a simple method and a device for unambiguously distinguishing dry roads from wet roads and icy roads. The method and device can be used to provide warnings to drivers, to provide information for automobile tracking systems, to provide information for automobile breaking systems, and to provide information for autonomous automobile systems, among other applications.
Dry roads can be distinguished unambiguously from icy roads, wet roads, and roads with layers of snow or water by measurements of the radiance in spectral bands in which the slope of the absorption of electromagnetic radiation by ice is substantially different from that of water.
In some embodiments of the present invention, detectors, detector arrays or multi-spectral cameras can be used to make the required measurements. A similar system can be used for detecting ice or water unambiguously on aircrafts, manufacturing systems, or any other object of interest.
In some embodiments of the present invention, a system is provided that is configured to detect water, snow, frost, clear ice (black or glaze ice), and other types of ices on roads and any other surface of interest. The system is configured to distinguish dry surfaces from those covered by water, snow, frost, and various types of ice even when they cover only a fraction of the field of view of the road condition monitoring system.
The monitoring of road conditions enhances the safety of motor vehicles by providing warnings to the driver, traction control, braking, cruise control, or automation systems. Moreover, the data from the measurements by the road condition monitoring system can be shared with connected vehicles and any other potential users, such as road maintenance departments.
Water and ice can often be difficult to detect by drivers or current synthetic vision systems. Clear ice (black or glaze ice) is unusually difficult to detect. Unfortunately, practical systems capable of reliably detecting ice or water on roads do not exist.
Cars, trucks, trains, automated people movers, rails, monorails, metros, buses, motorcycles, bicycles and other similar vehicles lack suitable systems for detecting the presence of ice or water on surfaces, such as roadways, bridges, railways, sidewalks, or even runway and taxiways (such as in connection with ground operations of aircraft or supporting personal and vehicles).
Ice detection in most vehicles merely includes a simple notification once the air temperature is at or near the freezing point of water. However, unfortunately, temperature is not a reliable indicator of the presence of surface ice that may affect the safety or drivability of a vehicle. The fact that drivers and operators are frequently unaware of the deteriorating road condition ahead of a vehicle frequently leads to accidents.
Some of the prior art approaches for detecting slippery ice on surfaces, such as roads, use an imager capable of measuring the polarization of the light reflected by glaze ice. However, it should be understood that although light is polarized when reflected by dielectric materials, such as glaze ice, glaze ice is not the only dielectric material that polarizes light. In fact, reflections by wet and/or oily surfaces and even smooth asphalt also cause polarization, which would lead to false reporting of the presence of ice. Therefore, polarization measurements are not enough for distinguishing among the possible types of dielectric materials scattering or reflecting light. Consequently, they cannot be used to detect the presence of ice or water unambiguously.
For example, U.S. Pat. No. 2008/0129541A1 refers to a slippery ice warning system capable of monitoring the road ahead of a vehicle. One or two cameras are used to image the same scene at two orthogonal polarizations. When a single camera is used, a polarization beam splitter is used to separate the reflected light into two orthogonal polarizations. The possible (but ambiguous) determination of the existence of slippery ice ahead of the vehicle is detected by measuring the polarization of the reflected light. However, again, this system is unable to discern whether the detected polarization is due to ice or some other reflective material.
Some of the prior art approaches for detecting ice and water on surfaces are also based on infrared radiance measurements. However, these prior art techniques are more complex and less accurate than the method described in the present disclosure.
For example, U.S. Pat. No. 2005/0167593A1 refers to a method that uses shift in the wavelength of the reflectance near 1.4 μm to distinguish water from ice. In this method, liquid water and ice are discriminated from each other by analyzing shifts in the short wavelength edge of the 1.4 μm band reflectance. This requires at least three measurements. The midpoint wavelength of the transition is compared to threshold ranges for ice and liquid water. The midpoint wavelength is mapped using at minimum the values of radiance measurements at three narrow bands near the step. Detection decisions are based on shifts in wavelengths, not the simpler ratio of radiance values of the present teachings.
According to the principles of the present teachings, a water, snow and ice detection system is provided that overcomes the disadvantages of the prior art and is particularly useful for the monitoring of road conditions. In most embodiments of the present teachings, the system detects ice, snow, and water unambiguously by making measurements of radiance. In some embodiments, the system can be passive while in other embodiments a light source can be included, multispectral detectors and/or multispectral camera, a data processor unit, and interfaces with displays, safety systems, and/or autonomous systems to provide an indication of the road condition and a response to it.
The road condition monitoring system of the present teachings can be passive and in one embodiment contains only a detector pair with filters, a data processor unit, and interfaces to displays or control systems.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.